Abstract:
The Mercator mission was defined in 1996 by six partner organizations (Cnes, CNRS, Ifremer, IRD, Meteo France, and Shom). Mercator Ocean is based in Toulouse, France, which acts as the focal point for development work. Today, the team numbers 30 engineers and researchers from the six partner organizations, supported by ... subsidiaries CERFACS and CLS, and occasionally by external computer services and engineering companies. The group is developing several operational systems at a time. Only one system is used within the Mersea strand1 context and is described below.

Mercator has been providing weekly analysis and real-time nowcast (T0), and forecast (T0+7 days and T0 +14 days) bulletins of the three-dimensional ocean in the North and tropical Atlantic up to 20 degrees S since January 17th 2001. The medium-resolution bulletin (1/3 degree; one point computed every 35 km at the equator) gives conditions from the surface right down to the bottom. This resolution is suitable for monitoring ocean circulation on a large scale. The first high-resolution bulletin (1/15 degree; one point computed every 5 to 7 km throughout the region of interest) was published on January 8th 2003 and is eddy-resolving. It covered the North Atlantic between 9 degrees N and 70 degrees N and the whole of the Mediterranean Sea. A low resolution global ocean model (2 degrees; one point computed every 220 km at the equator) with altimetry data assimilation is also available since May 2004. A high resolution global operational circulation model (1/4 degrees) assimilating satellite and in situ data is planned for the 2005 year. For more information see Mercator Configurations Summary at http://www.mercator-ocean.fr/html/mod_actu/public/welcome_en.php3

Additional information about the Model: --------------------------------------------------- The four ocean model configurations retained by the Mercator project are all based on the OPA z-coordinates ocean circulation model (Madec et al., 1998). OPA is an incompressible Navier-Stokes primitive-equation model using Boussinesq rigid-lid approximation that describes the temporal evolution of velocity, temperature and salinity in three dimensions. Mixed layer dynamic is ruled by TKE turbulent closure equations (1.5 closure scheme) (Blanke et al. 1993). The first model configuration is the "Maquette Atlantique Nord" (MNATL) between 20 degrees S and 70 degrees N. The second one is the "Prototype Atlantique Mediterranee" (PAM) between 9 degrees N and 70 degrees N. The horizontal resolution is 1/3 degree for MNATL, 1/15 degrees for PAM and 43 levels are used on the vertical for both of them. The bathymetry is processed from the Smith and Sandwell (1997) data base and ETOPO5. Momentum and heat forcings are daily ECMWF forcing. Surface temperature is restored from Reynolds analyses (Reynolds & Smith, 1994), which include satellite and in-situ observations. Surface salinity is restored from climatology. The model is initialized using Reynaud (Reynaud et al. 1998) seasonal climatology. At last, two Ocean Global Prototypes, POG (1/4 degrees, 43 levels) and ORCA (2 degrees, 31 levels) are being implemented.

Assimilation Method: -------------------------- The data assimilation method (SAM; Systeme d'Assimilation Mercator) used is the reduced-order optimal interpolation (OI) scheme SOFA (Sub Optimal Filtering of Altimetry) (De Mey and Benkiran, 2002) coupled with the PALM software coupler (PALM group, 2000). The baroclinic component is corrected applying a lifting-lowering method similar to Cooper and Haines method (1996). Data assimilation is stopped along isobaths 500m towards the coast. Sea level anomaly (SLA) from Jason1/ERS2-Envisat/GFO is assimilated along track, once a week. The mean sea surface height (MSSH) used during the assimilation process is the one from Rio et al. (2003) diagnosed from in-situ observations in the Atlantic ocean. In the Mediterranean basin, MSSH is made out of several numerical simulations. Version 1 products assimilates altimetry data (SLA) only, while version 2 products assimilates altimetry and in situ data (SLA, Sea Surface Temperature (SST), Sea Surface Salinity (SSS) and In situ profiles).

Mercator bulletins contain a range of parameters selected to depict ocean conditions and dynamics. These include: salinity, temperature, surface currents, zonal, meridian and vertical velocities, transport, sea surface height, mixed layer depth, barotropic height, baroclinic height. "Model: analysis and forecasting" 3D ocean products and "observed ocean" 3D products can be accessed on-line through Mercator Web Products (full domain and zonal animations, whole maps, zonal maps, sections and moorings graphs). The "observed ocean" system is based on altimetry and in situ data measurements. For additional product information see http://www.mercator-ocean.fr/html/produits/description/welcome_en.html). Mercator web products are designed for a wide audience (freely available), while numerical products are files for professional users and are available on a remote server. Please make an e-mail request to products@mercator-ocean.fr Archive bulletins are also available to identify longer-term patterns.

In the Mersea strand1 european project context, Mercator makes available via an DODS/Opendap server its PSY2 high-resolution prototype products since 01/06/2003. Mercator also offers access to its products via the LAS implemented in the Mersea context. For more information see http://strand1.mersea.eu.org/html/strand1/datalinks.html

Description:
Mercator Web products hanbook webpage (including the "Model: analysis and forecasting" products handbook and the "Observed ocean" products handbook). This handbook gives you the keys to understanding the 2,000 images you can see every week in the Mercator Web bulletin. The "observed ocean" system is based on altimetry and in situ data measurements. Additional information about Mercator configuration can also be found.

Access Constraints
Mercator web real time image products (GIF format) are designed for a wide audience (freely available, except zonal maps younger than 30 days need authorized access), while numerical products are files for professional users and are available on a remote server with authorized access.

Please, you must justify your request to these products. E-mail request to products@mercator-ocean.fr or download the form

Publications related to Mercator project in specialized reviews ----------------------------------------------------------------------- Davidson, F., Hernandez, F. and Rio, M.H. : Impact of a realistic Mean Dynamic Topography on the forecast capabilities of the Mercator operational model assimilation system of the North ... Atlantic. In prep.